Abstract: An image forming apparatus includes a photosensitive member, a charging roller, a cleaning roller, an urging member and an image forming portion. The charging roller has an outermost surface layer including an electroconductive resin material, first surface particles having an average particle size of more than 7 ?m and less than 30 ?m and second surface particles having an average particle size of more than 2 ?m and less than 6 ?m. The first and second surface particles are dispersed in the electroconductive resin material so as to form first projections and second projections, respectively. The cleaning roller cleaning roller includes a shaft portion and an elastic cleaning portion extending helically around the shaft portion and having a rectangular cross-section perpendicular to an extending direction thereof.

Abstract: An image forming apparatus includes a photosensitive member having a surface having elastic deformation power of 47% or more, a charging roller forming a nip between itself and the photosensitive member, and an image forming portion. When a nip region corresponding to the nip is formed and then an area of independent contact portions between the charging member and a measuring contact member is measured, the following relationship is satisfied: (contact width X)×(Contact area ratio ?)?0.1, where a length from a position of one end to a position of the other end of the nip region with respect to a direction perpendicular to a longitudinal direction of the charging roller is the contact width X, and a ratio of a sum of areas of the independent contact portions to an entire area of a measuring region is the contact area ratio ?.

Abstract: An image forming apparatus includes an image bearing member, a charging roller, a toner image forming portion, a voltage source, a detecting member, a controller, and a test executing portion configured to execute an operation in a test mode in which in a period in advance of the image forming period, a plurality of test AC voltages having a test peak-to-peak voltage with different frequencies are successively applied to the charging roller and alternating currents are detected by the detecting member. The test executing portion sets a predetermined peak-to-peak voltage on the basis of a specific frequency which is a maximum frequency at which a relationship between the frequencies and the alternating currents acquired in the operation in the test mode maintains linearity.

Abstract: A charging roller includes a surface layer containing first and second surface particles and satisfying the following: 6.0 (?m)?Rz?18.8 (?m),??i where Rz is a ten-point average roughness (?m) of a charging roller surface, 7 (?m)?d?20 (?m),??ii where d is a thickness (?m) of the surface layer, 9.8 (?m)?D1?15.8 (?m) and 2.8 (?m)?D2?5.2 (?m),??iii where D1 and D2 are average particle size (?m) of the first surface particles, and the second surface particles, respectively, 3.0?D1/D2?5.6, and??iv 0.10?M1/(M1+M2)?0.32,??v where M1 is a total weight (mg) of the first surface particles per unit area of the charging roller surface, and M2 is a total weight (mg) of the second surface particles per unit area of the charging roller surface.

Abstract: A charging roller includes a surface layer containing first and second surface particles and satisfying the following: 6.0 (?m)?Rz?18.8 (?m), ??i) where Rz is a ten-point average roughness (?m) of a charging roller surface, 7 (?m)?d?20 (?m), ??ii) where d is a thickness (?m) of the surface layer, 9.8 (?m)?D1?15.8 (?m) and 2.8 (?m)?D2?5.2 (?m), ??iii) where D1 and D2 are average particle size (?m) of the first surface particles, and the second surface particles, respectively, 3.0?D1/D2?5.6, and ??iv) 0.10?M1/(M1+M2)?0.32, ??v) where M1 is a total weight (mg) of the first surface particles per unit area of the charging roller surface, and M2 is a total weight (mg) of the second surface particles per unit area of the charging roller surface.

Abstract: An image forming apparatus includes a photosensitive member having a surface having elastic deformation power of 47% or more, a charging roller forming a nip between itself and the photosensitive member, and an image forming portion. When a nip region corresponding to the nip is formed and then an area of independent contact portions between the charging member and a measuring contact member is measured, the following relationship is satisfied: (contact width X)×(Contact area ratio ?)?0.1, where a length from a position of one end to a position of the other end of the nip region with respect to a direction perpendicular to a longitudinal direction of the charging roller is the contact width X, and a ratio of a sum of areas of the independent contact portions to an entire area of a measuring region is the contact area ratio ?.

Abstract: An image forming apparatus includes a photosensitive member, a charging roller, a cleaning roller, an urging member and an image forming portion. The charging roller has an outermost surface layer including an electroconductive resin material, first surface particles having an average particle size of more than 7 ?m and less than 30 ?m and second surface particles having an average particle size of more than 2 ?m and less than 6 ?m. The first and second surface particles are dispersed in the electroconductive resin material so as to form first projections and second projections, respectively. The cleaning roller cleaning roller includes a shaft potion and an elastic cleaning portion extending helically around the shaft portion and having a rectangular cross-section perpendicular to an extending direction thereof.

Abstract: An image forming apparatus includes an image bearing member, a charging roller, a toner image forming portion, a voltage source, a detecting member, a controller, and a test executing portion configured to execute an operation in a test mode in which in a period in advance of the image forming period, a plurality of test AC voltages having a test peak-to-peak voltage with different frequencies are successively applied to the charging roller and alternating currents are detected by the detecting member. The test executing portion sets a predetermined peak-to-peak voltage on the basis of a specific frequency which is a maximum frequency at which a relationship between the frequencies and the alternating currents acquired in the operation in the test mode maintains linearity.

Abstract: A developing apparatus includes a first chamber for accommodating a developer, the first chamber being provided with a developer carrying member for carrying the developer; a second chamber communicated with the first chamber through communication openings provided at opposite end portions to establish a circulation path; a feeding member, provided in the second chamber, for feeding the developer in a feeding direction which is from one of the communication openings toward the other communication opening; a sealing portion for openably sealing the communication openings; a moving mechanism for opening the communication openings by moving the sealing portion; and a reverse feeding member for feeding the developer in a direction which is opposite the feeding direction.

Abstract: An image forming apparatus includes: a drum; a charger; a developing portion; a transfer portion; a first adjuster; a second adjuster; and a controller for controlling the first and second adjuster. A first voltage is applied to the first adjuster during a period from a time when a rear end of a region in which an electrostatic image corresponding to a final image is to be formed passes through the first adjuster until a time when the rear end passes through the charger. The first voltage is lower in absolute value than a voltage applied to the first adjuster. A second voltage is applied to the second adjuster when a front end of a region of the drum opposing the first adjuster to which the first voltage is applied reaches the second adjuster. The second voltage is higher in absolute value than the voltage applied to the second adjuster.

Abstract: An image forming apparatus includes an image bearing member, a first toner charging member, provided downstream of a transfer device and upstream of a charging device with respect to a rotational direction of the image bearing member, for electronically charging toner remaining on the image bearing member, and a second toner charging member, provided downstream of the first toner charging member and upstream of the charging device with respect to the rotational direction, for electrically charging the toner remaining on the image bearing member by being supplied with a voltage of a polarity identical to a normal charge polarity of the toner. In addition, a controller controls application of a predetermined voltage to the first toner charging member, and a first AC voltage is applied to a developer.

Abstract: A phase synchronization mode is performed at a time of subsequent rotation after image formation. After detection of a phase difference by phase detecting sensors 103a, 103d, rotation phases are synchronized between driving motors 111, 102d after a lapse of a variable time. Specifically, timing for starting the rotation phase synchronization is shifted by 20 msec for each phase synchronization control so as to vary angular positions of the photosensitive drums 101a, 101b, 101d at which phase control is started. In this manner, sliding-contact positions are distributed and development and concentration of sliding-contact damages are prevented on the photosensitive drums 101a, 101b, 101d.

Abstract: An image forming apparatus includes an image bearing member; a brush roller, rotatable in a predetermined rotational direction, contacted to the image bearing member; and an applying device for applying a bias to the brush roller. The brush roller includes a shaft and a woven fabric brush including fibers planted in a strip-like base material, which is wound helically about the shaft with a helical winding gap. The woven fabric brush is subjected to fiber slanting processing so that the fibers of the helically wound woven fabric brush are slanted, so as to cover the helical winding gap, from a downstream side toward an upstream side with respect to a longitudinal direction in which a helically extending widthwise edge of the base material appears to be moving when the brush roller rotates in the predetermined rotational direction.

Abstract: An image forming apparatus includes a photosensitive member; a charging device for electrically charging the photosensitive member; an exposure device for exposing to light the photosensitive member charged by the charging device to form an electrostatic image on the photosensitive member; a developing device for developing the electrostatic image on the photosensitive member with toner to form a toner image; a transfer portion for transferring the toner image from the photosensitive member onto an image receiving member; a toner charging portion, disposed upstream of the charging device and downstream of the transfer portion with respect to a rotational direction of the photosensitive member, for electrically charging the toner remaining on the photosensitive member without being transferred onto the image receiving member; and control portion for controlling the charging device and the exposure device so that a stripe-shaped electrostatic image is repeatedly formed in substantially parallel to a longitudina

Abstract: An image forming apparatus includes: a drum; a charger; a developing portion; a transfer portion; a first adjuster; a second adjuster; and a controller for controlling the first and second adjuster. A predetermined voltage is applied to the first adjuster during a period from a time when a rear end of a region in which an electrostatic image corresponding to a final image is to be formed passes through the first adjuster until the time when the rear end passes through the charger. The predetermined voltage is lower in absolute value than a voltage applied to the first adjuster. An AC voltage is applied to the developing portion when a front end of a region of the drum opposing the first adjuster to which the predetermined voltage is applied reaches the developing portion. The AC voltage is higher in peak-to-peak voltage than the voltage applied to the developing portion.

Abstract: An image forming apparatus includes: a drum; a charger; a developing portion; a transfer portion; a first adjuster; a second adjuster; and a controller for controlling the first and second adjuster. A first voltage is applied to the first adjuster during a period from a time when a rear end of a region in which an electrostatic image corresponding to a final image is to be formed passes through the first adjuster until a time when the rear end passes through the charger. The first voltage is lower in absolute value than a voltage applied to the first adjuster. A second voltage is applied to the second adjuster when a front end of a region of the drum opposing the first adjuster to which the first voltage is applied reaches the second adjuster. The second voltage is higher in absolute value than the voltage applied to the second adjuster.

Abstract: An image forming apparatus includes a rotatable photosensitive member; a charging device for electrically charging the photosensitive member; a developing device for developing with toner an electrostatic latent image formed on the photosensitive member electrically charged by the charging device; a transfer device for transferring a toner image from the photosensitive member onto an image-receiving member; and an auxiliary charging device for electrically charging untransferred toner on the photosensitive member to a normal charge polarity before the photosensitive member is electrically charged by the charging device; wherein effective widths WPM, WCD, WDD, WTD, and WACD of the photosensitive member, the charging device, the developing device, the transfer device, and the auxiliary charging device satisfy: WPM>WCD>WACD?WTD>WDD.

Abstract: An image forming apparatus includes an image bearing member; a brush roller, rotatable in a predetermined rotational direction, contacted to said image bearing member; and an applying device for applying a bias to the brush roller. The brush roller includes a shaft and a woven fabric brush including fibers planted in a strip-like base material which is wound helically about the shaft with a helical winding gap. The woven fabric brush is subjected to fiber-slanting processing so that the fibers of the helically wound woven fabric brush are slanted, so as to cover the helical winding gap, from a downstream side toward an upstream side with respect to a longitudinal direction in which a helically extending widthwise edge of the base material is seen moving when the brush roller rotates in the predetermined rotational direction.

Abstract: A developing apparatus includes a first chamber for accommodating a developer, the first chamber being provided with a developer carrying member for carrying the developer; a second chamber communicated with the first chamber through communication openings provided at opposite end portions to establish a circulation path; a feeding member, provided in the second chamber, for feeding the developer in a feeding direction which is from one of the communication openings toward the other communication opening; a sealing portion for openably sealing the communication openings; a moving mechanism for opening the communication openings by moving the sealing portion; and a reverse feeding member for feeding the developer in a direction which is opposite the feeding direction.

Abstract: A phase synchronization mode is performed at a time of subsequent rotation after image formation. After detection of a phase difference by phase detecting sensors 103a, 103d, rotation phases are synchronized between driving motors 111, 102d after a lapse of a variable time. Specifically, timing for starting the rotation phase synchronization is shifted by 20 msec for each phase synchronization control so as to vary angular positions of the photosensitive drums 101a, 101b, 101d at which phase control is started. In this manner, sliding-contact positions are distributed and development and concentration of sliding-contact damages are prevented on the photosensitive drums 101a, 101b, 101d.